1. Field of the Disclosure The present disclosure relates to a brushless motor.
2. Discussion of the Related Art
Generally, almost every vehicle employs an electric power-assist steering system. Such an electric power-assist steering system generates an assist force based on the steering torque and the steering angle in order to enhance the steering performance of the vehicle.
That is, a steering system that assists a steering force of a vehicle with a separate power is used to enhance the motion stability of a vehicle. Conventionally, the auxiliary steering device uses hydraulic pressure, but an Electronic
Power Steering (EPS) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a viewpoint of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is configured such that an Electronic Control Unit (ECU) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The EPS system is also such that a motor assists a torque manipulating a steering wheel to allow a driver to steer a vehicle with less power, where the motor employs a Brushless Direct Current (BLDC) motor.
The BLDC motors have been increasingly used because the brushless motors are excellent in maintenance property, have a small size, and are capable of generating a high torque.
The BLDC motor generally forms an exterior look by coupling of a housing with a cover member, an inner circumferential surface of the housing is provided with a stator, and the stator is centrally formed with a rotor rotatably mounted in electrical interaction with the stator. The rotor is rotatably supported by a rotation shaft, and an upper surface of the rotation shaft is connected by a steering shaft of a vehicle to provide a power assisting the steering of the vehicle as mentioned above. The stator of EPS motor thus configured serves to supply an electric power to a wound coil via busbar.
The stator includes a core and a coil wound on the core, and in general, a motor used for a vehicle is employed with a plurality of coils connected in parallel for loss reduction. Thus, the coil is extended to an input/output terminal, and integrated and connected at the terminal during parallel connection. In order to integrate and connect the coil arranged in parallel, a busbar is coupled to an upper surface of the stator, and in order to couple the busbar, a coil terminal of coils respectively wound on the upper surface of stator, and the busbar is connected to the coil terminal.
The busbar is fixedly arranged with a plurality of metal members electrically connected to the coil terminal which is then insulated by an insulator. The busbar takes an approximate shape of a doughnut to correspond to a shape of the stator. The busbar is arranged at a periphery with terminals for connecting the coil terminal.
The shape of a busbar is change in response to a connected electrical power, and in general, the EPS motor is configured such that respective input/output terminals are sequentially arranged to a periphery of the busbar through a 3-phase circuit.
However, there is a disadvantage in a connecting process of a busbar to a coil, in a case the busbar is used to connect the coil, and in miniaturizing a motor because a height of an EPS motor increases as high as a height of the busbar.
Another disadvantage is that a processing time is excessively required to manufacture a busbar, because of a complicated process such as mold-formation of a busbar body using an insulator by formation of a busbar.